The present invention relates to a frame for partial illumination in photographic copying of negatives, diapositives and the like onto a copying paper.
Partial illuminating frames for such purposes are known in the art. A known partial illumination frame has a paper-receiving plate with a cover plate which lies on the paper-receiving plate and is operatively withdrawable from the latter. In the process of illumination of a partial face of a partial illumination frame, the copying paper is inserted into the frame and the paper-receiving plate is closed by the cover plate, whereafter an enlargement device is adjusted for focused projection. The focusing position is obtained on the upper face of the cover plate which is initially in the closed position, that is above the plane of the paper-receiving face of the frame. Thereby, a height differential takes place between the focusing plane and the paper-receiving face, which height differential corresponds to the thickness of the cover plate and leads to sharpness or focusing losses. This cannot be avoided even in the cases when the cover plate has a small thickness.
In another known partial illumination frame height adjustment is utilized, wherein the vertical position of the copying paper lying on the paper-receiving plate is taken into consideration, and the observe face of the enlargement device is adjusted relative to the same. The focus adjustment is performed here by an additional part which must be continuously exchanged relative to the partial illumination frame, whereby it can be misplaced or must be searched in darkness.